Canon Softness Just An Autofocus Problem?

Discussion in 'Canon' started by SneakyP, Jan 26, 2010.

  1. SneakyP

    SneakyP Guest

    I've had my DSLR entrant level for about 8 months now and only occasionally
    could I get a decent picture, from the stock kit lens, such as the
    following:

    http://i172.photobucket.com/albums/w4/ph0t0gra4/Referrals/_MG_3852.jpg

    [EF-S 18-55mm 3.5-5.6/f (stock kit lens), shot at 55mm, 7.1 1/200s]

    Upon testing the thought that lenses make a difference in focus quality, I
    interchanged between the kit lens and a much better quality L series
    telephoto- a 70-200mm; as well as another zoom 17-85mm lens, got a cleaner
    picture with a higher capture rate, but still the question is bugging
    me...

    More times than not, the pictures I take with that kit lens would turn out
    soft/slightly out of focus, and only rarely would I get pictures that
    focused in on the subject correctly, but yet the quality of the focus was
    still kind of soft. Question is for those who have experiences with using
    that AF in Canon cameras, is that out-of-focus/softness typical of Canons
    in an auto-focusing mode? Is the lens making that much difference as far
    as successful AF focusing goes?
     
    SneakyP, Jan 26, 2010
    #1
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  2. SneakyP

    Peabody Guest

    I have no such experience, but have read there is an ongoing
    issue with autofocus problems with the Canon XSi. It's
    possible it might be the same issue with your XS. If you
    consistently get good focus manually, but poor focus in AF,
    you might want to talk to Canon about sending it in for
    warranty repair before the year is up.

    I've seen AF problems blamed on the lens, but it seems to me
    that the focusing sensor is in the camera body, so it's the
    camera that decides when the subject is in focus - that's
    the control point in the feedback loop. The focusing motor
    may be in the lens, but the camera controls it. Well, maybe
    one of the experts here can clear this up.

    In any case, I would seriously consider having a long talk
    with Canon service about the AF problem. I don't think
    there should be any consistent difference between AF and
    manual results.
     
    Peabody, Jan 26, 2010
    #2
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  3. SneakyP

    DSLR Honesty Guest

    No, this is what you get for listening to the advice of all the dSLR-Trolls
    that don't know shit about cameras and photography. A pricey lesson for
    you, a non-liable risk-free laugh for them.
     
    DSLR Honesty, Jan 26, 2010
    #3
  4. SneakyP

    Bob Williams Guest

    It is a FEATURE.
    Especially useful for portrait photography of ugly people....;-)
    Bob Williams
     
    Bob Williams, Jan 26, 2010
    #4
  5. SneakyP

    AnthonyL Guest

    It would have helped to have said which camera
    Did you apply any sharpening to this picture? I've downloaded it and
    a bit of sharpening does help.
    ok, so this is not the IS version. In general this lens does not have
    a great reputation whereas the 18-55 IS is generally well regarded
    (value form money)
    That's not surprising

    Which focus points are you using? You need to be careful in the photo
    you took that the focus is on the eyes and the camera is not being
    tricked into trying to focus on the hand.
    I think the Canon rule is that the non-L lenses should autofocus
    within 1 DOF and the L lenses should autofocus to 1/3 DOF. So cheaper
    lenses need not put the same plane in focus every time.

    Does your camera have flash autofocus assist? Otherwise in low light
    focussing is also less accurate.

    Best to go over to the Canon forums in www.dpreview.com for a wider
    range of input though if you google search

    rebel xs 18-55 focus site:forums.dpreview.com

    you'll get some hits on this.

    Good luck.
     
    AnthonyL, Jan 26, 2010
    #5
  6. SneakyP

    Good Info Guest

    An isolated incident.

    See this page where a Canon Powershot SX10 beats the image quality from a
    Canon EOS 450D DSLR. The SX10's 20X zoom lens clearly beating the more
    simpler to create 3X zoom lens of the DSLR in resolution and CA
    performance.

    <http://www.cameralabs.com/reviews/Canon_PowerShot_SX10_IS/outdoor_results.shtml>

    Or these pages where Powershot G-series P&S cameras compete with a medium
    format Hasselblad and actually beat the images from a Canon 7D DSLR in
    resolution and image quality.

    <http://www.luminous-landscape.com/reviews/kidding.shtml>

    <http://darwinwiggett.wordpress.com/2009/11/11/the-canon-7d/>

    I'd have Canon check out that camera if I were you.
     
    Good Info, Jan 27, 2010
    #6
  7. SneakyP

    Peabody Guest

    Scott W says...
    Can you explain to me why it would be the lens's fault that
    autofocus is soft? If the lens is crisp in manual focus,
    but soft in autofocus, wouldn't that be a camera body
    problem? My understanding is that the autofocus sensor is
    either the main sensor or a separate focus sensor inside the
    camera, and the lens only has a motor that moves the lens
    element(s) in and out - as controlled by the camera, but has
    no "smarts" at all. Is that wrong?
     
    Peabody, Jan 28, 2010
    #7
  8. And the lens reports offsets and focus shifts due to aperture
    settings ... and these can be off as well, so the lens can be
    at fault.

    -Wolfgang
     
    Wolfgang Weisselberg, Jan 28, 2010
    #8
  9. SneakyP

    Ray Fischer Guest

    Canon actually puts processors in their lenses. That's how the
    cameras can tell what lens is attached and what its current focal
    length is.

    Sloppy motors, gears, whatever, can make the focusing inconsistent.
     
    Ray Fischer, Jan 29, 2010
    #9
  10. SneakyP

    Paul Furman Guest

    There's nothing inherently wrong with Canon or Nikon, they should be
    generally comparable. Can you post some samples, with full size crops,
    or full image?

    What Nikon lenses do you have? They may be worth using on digital.
    Possibly more useful on a Canon body, it depends on the specific lens.
     
    Paul Furman, Feb 6, 2010
    #10
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